1. Field
The present disclosure relates to tires for running on ice that include studs (i.e. “studded tires”).
2. Description of Related Art
Studded tires have undeniable advantages in terms of behavior in winter driving conditions, such as for example driving on an icy surface. Contact with the ice, and more particularly penetration of the studs into the ice, compensates for observed reduction in grip of the tread pattern elements of the tire. The studs scratch the ice and generate additional forces on the ice.
One of the difficulties in using studded tires consists of the fact that these tires, when used on a non-icy road, degrade the surface condition of the road and lead to premature wear of the roadway. It is for this reason that a number of countries have prohibited studded tires or have limited their use to certain types of vehicle and/or to limited periods.
It has been proposed (see Japanese patent JP 63-297109) to reduce this problem by combining the studs with bearing elements made of a rubber composition that are deformed when a radial force is exerted on the studs. The rubber composition of which these bearing elements are made is chosen so that their resistance to deformation increases when their temperature drops. If the tire is running on ice, the temperature of the bearing element is low and its resistance to deformation is high. Consequently, the bearing element withstands the force transmitted by the stud and protrudes from the tread, so as to scratch the ice. In contrast, when the tire is running on a non-icy roadway, the temperature of the bearing element is higher and it has a lower resistance to deformation. Consequently, the studs may disappear into the tread each time that they come into contact with the roadway.
Although this approach has enabled the negative effect of studded tires on roadways to be reduced, the Applicant has found that the proposed solution is still insufficient as the point of operation of the studded tire is not optimized.
It has also been proposed (document JP 58 051134) to vulcanize the studs in a cube of rubber composition in a first stage and to stick or vulcanize this composite in the tread. The reader who wants to know other documents defining the technological background of the invention, will consult with profit documents EP 1 055 509 and DE 10 2010 015939.